Complexation of Oxonium and Ammonium Ions by Lower-rim Calix[4]arene Amino Acid Derivatives

Požar, Josip and Horvat, Gordan and Čalogović, Marina and Galić, Nives and Frkanec, Leo and Tomišić, Vladislav (2012) Complexation of Oxonium and Ammonium Ions by Lower-rim Calix[4]arene Amino Acid Derivatives. Croatica Chemica Acta, 85 (4). pp. 541-552. ISSN 0011-1643

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Abstract

Complexation of oxonium and ammonium cations with two calix[4]arene amino acid derivatives, namely 5,11,17,23-tetra-tert-butyl-26,28,25,27-tetrakis-(O-methyl-D-α-phenylglycylcarbonylmethoxy)-calix[4]arene (1) and 5,11,17,23-tetra-tert-butyl-26,28,25,27-(O-methyl-L-leucylcarbonylmethoxy)calix[4]¬arene (2), in acetonitrile and methanol was studied by means of spectrophotometric and calorimetric titrations at 25 °C. The classical molecular dynamics simulations of the macrocycles and the corresponding complexes with NH4+ and H3O+ were carried out in order to investigate their possible structures in solution. The examined calix[4]arene derivatives were shown to be rather efficient binders for H3O+ cation and moderately efficient for NH4+ in acetonitrile, whereas the complexation of these cations in methanol could not be observed. The structures of the complexes obtained by means of molecular dynamics simulations suggested the involvement of ether and carbonyl oxygen atoms in the complexation of both NH4+ and H3O+. An inclusion of an acetonitrile molecule into the hydrophobic cavity of the free and complexed ligands was observed as well. The difference in binding affinities of 1 and 2 towards NH4+ and H3O+ ions could be explained by taking into account cation solvation, difference in their size and in the strength of hydrogen bonding between cations and the ligand binding sites.

Item Type: Article
Keywords: calixarenes; oxonium cation; ammonium cation; complexation; solvation; microcalorimetry; UV spectrometry; molecular dynamics
Date: 2012
Subjects: NATURAL SCIENCES > Chemistry
Divisions: Faculty of Science > Department of Chemistry
Publisher: Hrvatsko kemijsko društvo
Related URLs:
Depositing User: Branka Maravic
Date Deposited: 07 May 2014 12:36
Last Modified: 07 May 2014 12:36
URI: http://digre.pmf.unizg.hr/id/eprint/1057

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